Image-based and in-situ measurement techniques for the characterization of the damage behavior of additively manufactured lattice structures under fatigue loading

Abstract

For a safe application of additively manufactured (AM) lattice structures in e.g. load-bearing implants, a comprehensive understanding of fatigue processes is required. With additional systematic investigations of the underlying fatigue behavior, the AM lattice structure design as well as a reliable estimation of their lifetimes can be facilitated. Therefore, nondestructive testing methods, digitalization of measurement techniques as well as signal processing can be combined with experimental routines in order to aquire more information about the fatigue process. In this paper, different designs of Ti6Al4V lattice structures with cubic unit cells were fabricated by electron beam melting. To investigate the fatigue process as well as the underlying fatigue behavior the lattice structures were tested in cyclic bending as well as torsion tests. The digital image correlation technique, temperature field measurement and potential drop method were implemented into the test rigs and tested for the characterization of the fatigue damage behavior as well as failure mechanisms. To distinguish the failure behavior in dependence of manufacturing related imperfections a microstructural analysis was performed. Therefore, some experiments were stopped in dependence of the measured potential and examined in micrograph analysing. The successful application of the measurement techniques allows an insight into the damage behavior as well as underlying failure mechanisms of 3D printed lattice structures under fatigue loading. Moreover, the identified results provide the basis for the validation of subsequent numerical simulations using local damage approaches.